Video transmission apparatus for connecting to a network

Abstract

A video transmission apparatus for connecting to a network has a peripheral block including a video processing unit for generating compressed video data of video signals and a network control unit for controlling transmission and reception of compressed video data through a transmission medium such as a network, and a central processing unit block including a storage unit for storing the compressed image data, a central processing unit for executing data processing and a central control unit for controlling each of these units in cooperation with the central processing unit, each of the units inside the peripheral block and inside the central processing unit block is successively connected in series by first and second buses, and the first and second buses are connected through a bus buffer.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates to a video transmission apparatus connected to a network. More particularly, this invention relates to a video transmission apparatus for increasing a quantity of data that can be transmitted through a network.[0002]A video transmission apparatus for connecting to a network converts video signals taken by an imaging device such as a camera from analog signals to digital signals (A / D conversion) and acquires video data. Each frame of the video signal constitutes this video data, and data compression is made by a video coding system such as JPEG (Joint Photographic Experts Group), for example. The compressed video data so obtained is transmitted to a reception apparatus connected to a transmission medium such as network typified by LAN (Local Area Network) and WAN (Wide Area Network). Further, the video transmission apparatus for use with a network receives the compressed video data from the transmission medium such as the networ...

AI Technical Summary

Benefits of technology

[0009]A method that makes up for the drop of processing efficiency of CPU employs CPU having a higher processing speed and a storage device accessible at a higher speed (for example, a memory capable of burst transmission in synchronism with a clock) and improves a data transmission rate on a system bus. When the transmission rate on the system bus is improved, however, influences of signal refection that incurs data error on a transmission path and cross-talk noise appear as distortion of a signal waveform due to various factors such as the relation between a signal rise or fall time and a signal propagation time and packaging of a signal wire of the system bus.

[0012]To transmit a signal at a high transmission rate, it is necessary improve the driving capacity of the driver40d and to much more shorten the rise time tr or fall time tf of the pulse waveform driven on the bus. Then, the reciprocation time τ required for the signal of the pulse waveform driven from the driver 40d to reciprocate on the signal line 40s to the receiver 40r sometimes becomes longer than the rise time tr and the fall time tf of the signal of the pulse waveform driven by the driver 40d shown in FIG. 6B. In such a time relationship of τ>tr, tf, the signal reaches the reception end (input point c) of the receiver 40r after its fall and is reflected. In consequence, undulating under-shoots 42u and 43u and undulating over-shoots 42v and 43v occur at the input point c in FIG. 6C. Similar phenomena occur after the signal rise, too. When the receiver 40r receives the signal of the pulse waveform shown in FIG. 6C and the signal exceeds a threshold value of a signal level of the receiver 40r in a time zone of the occurrence of the over-shoots 42v and 43v, signals as noises 44n and 45n shown in FIG. 6D occur. As a result, a data error or a factor inviting an unstable operation of the circuit occurs on the reception side. Though this explanation deals with the occurrence of the noise after the signal fall, similar data error and factor for the unstable operation of the circuit likewise occur due to the undulating distortion of the pulse waveform after the signal rise.

[0016]When the transmission data quantity to one user is doubled to obtain high-quality reproduction images on the reception side under such a processing capacity of CPU, the number of users to which the compressed video data of 30 fps can be simultaneously transmitted is at most one user, and the video transmission service drops. If the number of transmissible users is doubled to four users, on the contrary, the data quantity transmissible to one user drops to the half, and only reproduction images of low image quality can be acquired. Alternatively, there is a method that reduces the frame rate from 30 fps to 15 fps. This method can secure image quality of each frame though the number of frames decreases. However, this method is not free from the problem that the reproduction images become unnatural in the case of images having motion.

[0017]It is an object of the present invention to provide a video transmission apparatus for connecting to a network that improves transmission services by increasing the transmissible data quantity of images taken by a camera through a network.

[0026]To reduce signal reflection and unnecessary radiation, a dumping resistor is preferably connected to the starting point or the end point of each of the first and second buses, and a terminating resistor is preferably connected to the other.

Problems solved by technology

CPU has also to cope with irregular processing requests of input / output, and since data transmission or data processing is temporarily interrupted, processing efficiency of CPU drops.

When the transmission rate on the system bus is improved, however, influences of signal refection that incurs data error on a transmission path and cross-talk noise appear as distortion of a signal waveform due to various factors such as the relation between a signal rise or fall time and a signal propagation time and packaging of a signal wire of the system bus.

The occurrence of reflection invites the occurrence of distortion of the waveform such as overshoot and under-shoot in the transmission signal, a data error beyond a threshold value for identifying the signal, cross-talk noise and eventually, an unstable operation.

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